Door control system



Dec. 23, 1969 M. M. CHECK DOOR CONTROL SYSTEM 3 Sheets-Sheet 1 Filed July 24, 1967 INVENTOR MATHIAS M. CHECK ATTORNEY Dec. 23, 1969 M. M. CHECK DOOR CONTROL SYSTEM 3 Sheets-Sheet 2 Filed July 24, 1967 Dec. 23, 1969 M; M. CHECK- DOOR CONTROL SYSTEM 3 Sheets-Sheet 3 Filed July 24, 1967 FIG.5

United States Patent 3,484,991 DOOR CONTROL SYSTEM Mathias M. Check, 34 Bowman Drive, Greenwich, Conn. 06830 Filed July 24, 1967, Ser. No. 655,507 Int. Cl. E051? 15/02 US. Cl. 49-137 12 Claims ABSTRACT OF THE DISCLOSURE A door pivotally swinging with shaft 12 (FIG. 1) is spring biased to the closed position for either direction of opening by a single spring 34 operating through separate tension linkages respectively including links 32 and 36. Spring 34 maintains the door in a centered closed position as shown. The door may be power operated by fluid applied to cylinder 20. During power operation, return control vents from cylinder 20 are closed by ball valve 56.

This invention relates to an improved door control system of the type employing spring forces and hydraulic apparatus for control of the door operation. The invention is particularly useful in combination in a powered door operator system.

The need for the effective control of the operation of doors for buildings has been long recognized, particularly for public buildings where a high traffic density requires frequent opening and closing operation of the doors. More recently, door control systems for such purposes have been combined in power operated door apparatus in which a pedestrian approaching the door to the public building actuates the door operator system by interruption of a photoelectric light beam, by closing a switch built into a rubber floor mat, or by other means. Such systems are commonly hydraulically operated. The initial actuation of an electrical circuit by the pedestrian opens a hydraulic valve, or starts a hydraulic pump, or both, and the resultant flow of hydraulic fluid operates upon a piston which is connected through mechanical linkages to swing the door open. The opening operation of the door must be smooth and quiet, and the door must be automatically closed in a smooth and quiet manner after the pedestrian has passed through. These power operated door systems are often employed at entrance doors as well as exit doors, particularly in commercial establishments where it is important to encourage the entrance of customers. As a matter of convenience, the door always swings away from the pedestrian as he approaches. This means that a power operated entrance door swings inwardly under power actuation.

One of the important problems encountered in door control systems of the type described above is that all of the doors must be capable of swinging outwardly as emergency exits from the building in case of a fire or other emergency condition requiring rapid and unobstructed passage for the occupants of the building. For the entrance doors which swing inwardly, this means that the door must be capable of manual operation in the direction opposite to the power operation, that is, swinging outwardly. Furthermore, the'manual operation in the outward direction must not require an unreasonable operating force which a normal building occupant would not be capable of providing. Various approaches have been made to this problem. One common approach is to provide a release mechanism which releases the door from the control and positioning function of the power operator whenever a sufiicient force is provided to move the door in the direction opposite to the power operated direction. In such a system, when once released, the reverse operation of the door is virtually free of any restraint, and

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free from any automatic closing forces. Such a system is illustrated, for instance, in US. Patent 3,210,065, issued Oct. 5, 1965 to I. M. Linder et al.

A system of that type is very effective in satisfying the basic objective of permitting emergency exit. However, there are several major problems. One of these problems is that when the door is new, the initial release force for reverse operation may be rather high so that only a large individual having substantial weight and strength can actuate the door. This substantially reduces the safety which is supposed to be provided by the reverse operation feature. However, these door release mechanisms tend to wear rapidly when operated in the reverse direction so that the required release force may be substantially reduced to a point where mischievous children are able to operate the door much too easily, and accidental operation in the reverse direction may occur. But, one of the most annoying disadvantages of that prior arrangement is that there is no automatic return operation so that when the door is once released for operation in reverse, it simply remains open, exposing the interior of the building to the elements until someone manually moves it to the closed position.

These disadvantages are avoided in at least one prior automatic door operator system design by providing a separate spring which opposes the reverse door operation during the full reverse opening swing of the door, and which provides a reclosing force to the door to automatically close it after it has been operated in reverse. Such a system is illustrated, for instance, in US. Patent 2,911,210, issued Nov. 3, 1959 to H. W. Ferguson. However, the structure of that system requires a number of complexities which make it difiicult to adjust and maintain. Furthermore, a considerable starting force is required to commence the opening operation of the door. This is true both for the powered operation in the forward direction, and for the manual operation in the reverse direction.

Accordingly, it is an object of the present invention to provide an improved door control system which is simple, reliable, economical in construction, and which is particularly characterized by the elimination of components which require critical adjustments in prior structures while at the same time satisfactorily accomplishing all of the desired functions.

It is another object of the present invention to provide an improved door control system having a reduced physical size without impairing performance. Among the other advantages of reduced size, a smaller access plate is required, making the unit less conspicuous.

It is another object of the present invention to provide an improved door control system which is simplified by the provision of a single spring return system which is operable for both directions of swing of the door.

In prior door controllers, and particularly in power operated door control apparatus, it has been customary to apply a substantially uniform high closing spring force over at least the last portion of door travel to the closed position. The maintenance of the high spring force up to the point of complete door closure places heavy reliance upon the hydraulic damping apparatus associated with the door control mechanism for decelerating the door to stop it in the closed position. Furthermore, in either the motor operated mode of opening under power, or the manual reverse operation, the force opening the door must overcome the full force of the closing spring as well as the static inertia of the door in order to begin the opening movement.

Accordingly, it is another object of the present invention to provide an improved door control system which may be combined in a power operated door apparatus in which the final spring forces for centering the door are of reduced magnitude to thereby provide for smoother closing and easier opening.

In some prior art door closing structures having spring return from either opening position, very elaborate stop devices are provided, having complicated adjustment features to determine the final stopping position of the door.

It is another object of the present invention to provide a simplified door operating apparatus in which the need for elaborate stop mechanisms is eliminated.

As previously described, power actuated door openers are commonly powered by means of a hydraulic piston supplied with hydraulic fluid, usually a mineral oil, and generally referred to hereinafter as simply oil. The oil under pressure is supplied from a suitable pressure source generally including an electrically driven pump. For the return operation of the door, the piston cylinder is generally vented to permit the escape of oil from the cylinder at a controlled rate to thereby control the speed of door closure. These oil vents are not required during the opening operation and they simply constitute leaks of the precious oil under pressure, thus requiring a higher capacity hydraulic pressure fluid source. In such systems, it has previously been proposed to provide a hydraulic control valve which detects the presence of input pressure and which closes the vents of the cylinder during the opening operation of the door. Such a system is illustrated, for instance, in US. Patent 3,302,330-Loftus wherein the control valve just referred to is illustrated in FIG. 2 at 50. This valve structure is effective for reducing the leakage through the valve ports, but it is large, complicated, and expensive in construction. However, the spool valve provided in that structure cannot stop the leakage, and only reduces it.

Accordingly, it is another object of the present invention to provide an improved power operated hydraulic door opener having a vented power cylinder and providing an improved automatic vent closing valve operable during the power stroke in which the vent closing valve is substantially improved over similar prior structures particularly in terms of small size, simplicity, economy of construction, maintenance-free operation, and in providing complete vent closure.

In carrying out the invention in a preferred form thereof, there may be provided a spring restrained door control system including a pivoted shaft arranged to be connected to the door for rotation during swinging movement of the door. The shaft includes crank arms arranged on its opposite sides and separate collapsible tension linkages connected to each of the crank arms and extending away from the crank arms in substantially the same direction. Each of the collapsible linkabes is operable for controlling the rotation of the shaft in a direction opposite to the direction controlled by the other of the link ages. A single spring member is connected to both of the tension linkages to maintain them both in tension at a centered position of the shaft corresponding to a closed position of the door. The linkages are respectively operable to apply a tension force between the associated crank arm and the spring member upon rotation of the shaft in each of the two respective rotational directions. Each of the linkages is arranged to collapse whenever the shaft is a direction opposed by the tension in the other of said linkages.

In the accompanying drawings:

FIG. 1 is a top view of a door control system apparatus in accordance with the present invention with the cover plate of the casing removed.

FIG. 2 is a sectional side view of the embodiment of the apparatus illustrated in FIG. 1 but with the cover in place.

FIG. 3 is a detail view of portions of the tension linkages of the apparatus of FIG. 1 illustrating how the centered position of the door may be adjusted by means of a sh m.

FIG. 4 is a detail view of an alternative embodiment for the tension linkage members illustrated in FIG. 3, and

FIG. 5 is a sectional detail view of a portion of the cylinder block in the apparatus of FIG. 1 illustrating the construction of a cylinder bleeder valve vent arrangement including a ball valve operable for closing the cylinder vents during power opening of the door.

Referring more particularly to FIG. 1, the apparatus includes a casing 10 which is preferably arranged to be installed in a well in the floor beneath the door wiih which it is to be associated. Crank shaft 12 has an upper end which extends through the casing and is engaged for rotation with the door to be controlled (not shown). The crank shaft 12 is arranged for clockwise rotation by forces transmitted to a crank portion 14 thereof by means of a connecting rod 16 from a piston 18. The piston 18 is actuated by hydraulic fluid under pressure within the associated cylinder 20. The fluid under pressure is supplied from a standard source (not shown) through a supply tubing 22.

The opening operaion is smooth, being restrained by retarding forces transmitted to a crank portion 24 of crank shaft 12 by a connecting rod 26 and a piston 28 which is operable to reduce the volume within an associated cylinder 30 as the door swings open.

A tension linkage including a main link 32 is connected between the crank shaft 12 and a rotational tension spring 34 so as to provide spring forces to resist the opening movement of the door, and to automatically close the door when the supply of fluid pressure is interrupted. The apparatus is illustrated in FIG. 1 in the normal at rest position with the door closed. If the door is opened manually in the reverse direction, a tension linkage having a main link 36 restrains that motion and returns the door to the closed position by means of force from the spring 34.

The structure and operation of the apparatus will now be described in somewhat greater detail. The pressure fluid pipe 22 communicates with the cylinder 20 by means of a pipe fitting 38 which attaches to the cylinder block 40. Block 40 may be a common cylinder block for both of the cylinders 20 and 30. Pipe fitting 38 includes a ball check valve 42. which is arranged to open to admit hydraulic fluid from the pipe 22 into the cylinder 20. However, it closes to check reverse flow into pipe 22 whenever the flow from pipe 22 to cylinder 20 is interrupted. The cylinder housing 40 includes adjustable discharge ports for the cylinder 20, and having needle valve adjustments at 44 and 46. These discharge ports are shown in greater detail at 48 and '50 in FIG. 2. Both of the ports 48 and 50 discharge through a common discharge passage 52 and a common discharge port 54. The discharge passage 52 is arranged to be closed by a ball valve 56 whenever input pressure is present on the supply pipe 22 as detected through a passage 57. The ball valve 56 and the associated portions of the cylinder block 40 are shown in an enlarged detail in FIG. 5, and described more fully below in connection with that figure.

Referring briefly to FIG. 2, the bottom of the casing 10 is shown at 58, and the top is shown at 60, and these parts of the casing 10 are normally arranged horizontally. The interior of the housing 10 is normally almost completely filled with oil up to a level defined by a discharge pipe connection fitting indicated at 62. Outlet fitting 62 includes a ball check valve 63 permitting outward flow of oil, but preventing inward flow of oil. This is a precaution against an error such that the source of oil under pressure from 22 is accidentally connected to outlet fitting 62 instead of to the inlet fitting 38. In such a situation, without the provision of the check valve 63, the oil pressure is applied to the entire interior of casing 10 and will cause the casing to rupture and leak.

For the purpose of simplifying the drawing, the liquid level at outlet fitting 62 is not indicated in FIG. 2, but it will be understood that the entire cylinderblock 40, and

the lower major portion of crank shaft 12, and virtually all of the mechanism illustrated in FIGS. 1 and 2 are normally completely submerged in oil or hydraulic fluid. Thus, referring again to FIG. 1, cylinders 20 and 30 are both normally completely filled with oil.

The cylinder 30 is provided with exhaust ports associated with vents 64 and 66 for venting the cylinder 30, and which exhaust directly through the side of the cylinder 30, and which exhaust directly through the side of the cylinder block 40. These vents are adjustable by means of needle valves indicated adjacent to the respective vents and similar to the adjustable needle valves 44 and 46 for cylinder 20. During power operation when the displacement within cylinder 20 is increasing, the displacement within cylinder 30 decreases to provide a retarding effect upon the door. The rate at which the door is permitted to move, and the retarding effect of the pision 28 in the cylinder 30 is determined by the adjustments of the valves at the respective vents 64 and 66. Until the piston 28 reaches the cylinder port associated with vent 64, the rate of movement is determined by the rate at which oil can be discharged through both of the vents 64 and 66. At that point, the port associated vent 64 is closed by the piston 28, and from then on, the speed of movement is necessarily reduced to correspond to the discharge rate permitted by the vent 66 alone. This assists in deceleration of the opening movement of the door so that it does not hang into its stops at the fully opened position.

The needle valves such as 44 and 46 for cylinder 20, and the needle valves associated with ports 64 and 66 for cylinder 30 are preferably frictionally restrained in their adjusted positions by means of spring clips 65 and 67.

The piston 28 is provided with a built-in ball check valve 68 which automatically closes during the power opening operation in which the displacement within the cylinder 30 is being reduced. However, on the back stroke of piston 28, when the door is closing under the force of spring 34, and during which the displacement within cylinder 30 is increasing, the ball check valve 68 opens freely to allow the cylinder 30 to refill with oil. Thus, there is no substantial retardation by the piston 28 of the reclosing movement of the door. However, at the time when the reclosing cycle begins, and the flow of oil through the pipe 22 is discontinued, the ball check valve 42 closes to prevent oil from being pumped from cylinder 20 back through supply pipe 22. Also, the ball valve 56 opens the vent 54 to thus vent the ports 48 and 50 through needle valves 44 and 46 and the passage '52 to permit discharge of oil from cylinder 20. Thus, the reclosing operation of the door under the force of spring 34 is retarded and smoothly controlled by the rate of discharge of oil from the cylinder 20 through ports 48 and 50. At the beginning of the return stroke, the retarding force and the speed of operation are determined by the combined oil volume rate capacity of both ports 48 and 50 as determined by the adjustments of the needle valves 44 and 46. However, the rate is then reduced to the capacity only of vent port 50 as soon as port 48 is closed off by the piston 18.

The piston 18 is provided with a builtin ball check valve similar to ball check valve 68 shown and described above for piston 28. The ball check valve feature is omitted from the drawing for piston 18 for purposes of simplicity and clarity. The ball check valve within piston 18 is automatically closed during power operation when oil under pressure is supplied through pipe 22 to cylinder 20. It also remains closed during the normal reclosing operation when the displacement of cylinder 20 is being decreased by the return of piston 18. However, it is one of the features of the controller of the present invention that the door may be operated in the normal direction under manual force against the reclosing forces of the spring 34. When this occurs, the ball check valve within piston 18 automatically opens to permit the increased displacement of cylinder 20 to be filled with oil without undue restriction. During such operation, a normal resisting or retarding force is provided by the piston 28. Similarly, when the door is manually operated in the reverse direction, the displacement within piston 30 increases and is supplied with oil without restriction through the open ball check valve 68. A retarding force is provided by the reduction in displacement of cylinder 20 in accordance with the rate of discharge through the associated vent port 50.

The maximum excursion of the crank 12, and the door to which it is connected, is preferably controlled by means of a crank arm 70 equipped with adjustable stop members which are arranged to engage stop shoulders 72 and 74 in the associated corners of the casing 10. The door itself may be provided with its own stops also.

The tension linkage including main link 32 is pivotally attached to the crank 12 at 76, and includes links 78 and 80 pivotally connected together at 79 and to the main link 32. This linkage continues at the other end of main link 32 with a pivot connection at 81 to another pivoted link 82, and thus to a common link 84, which is pivotally connected to a rotating crank member 86. Crank 86 is attached to the upper end of the spring 34 by means of an integral tongue portion which is engaged by an end hook 88 formed as part of the spring 34. The bottom end of the spring 34 is similarly anchored to the casing 10 so that clockwise rotation of the crank arm 86 is resisted by torsion forces within spring 34, the clockwise rotations causing the spring 34 to be wound up.

The tension linkage including main link 36 is substantially similar to the tension linkage including main link 32. Thus, it includes a pivotal connection. of a link 92 to crank 12 at 90, and a pivotal connection at 93 to link 94, and thus to main link 36. At the other end of main link 36, there is a pivotal connection at 95 through a link 96 to the common link 84. During the normal at rest condition when the door is closed, both of the linkages including main links 32 and 36 are in tension imposed by an initial loading of spring 34. The opposing forces applied at the opposite sides of crank 12 by tension in these linkages hold the door in the proper centered and closed position. An adjusting means providing for slight angular adjustment of the door with respect to the crank member 12 is normally provided at the bottom edge of the door itself in accordance with conventional practice and is not shown in the present drawings. An acceptable form of that adjusting feature is illustrated in connection with a prior invention in US. Patent 2,673,367Ferguson.

As previously mentioned, during the normal power opening operation of the door, the linkage including main link 32 imposes a continuing restraining and returning force from the spring 34 to the crank member 12. During the initial portion of this operation, the tension on link 36 is gradually released, and the tension on link 32 is gradually increased until the forces previously shared between them from spring 34 are all taken by link 32. While this shift is occurring, the common link 84 rotates slightly in a clockwise direction to the point where the connection pivot 81 is positioned in substantially a straight alignment between the crank pivot and the link pivot 79 at the crank 12. The common link 84 and the link 82 are substantially locked together, and essentially form a single link in the above-mentioned operation. The link 78 which is attached to crank shaft 12 at pivot 76 essentially forms a part of crank shaft 12 when the associated linkage is in tension because link 78 is then pulled tight against an associated shoulder of the crank 12. The link 78 thus essentially forms a crank arm of crank shaft 12, and having an effective crank arm pivot at 79.

As the door opening operation continues, the opposite linkage including main link 36 collapses at the short links 92, 94, and 96 to accommodate for the clockwise rotational movement of crank 12 and the displacement of the common link 84 towards the crank 12. In this mode, it simply acts like a slack rope or cable. However, as soon as the door closes, the slack linkage is immediately realigned and re-tensioned as shown in the drawing. For re verse opening of the door, the linkages behave in a similar manner. Thus, the link 36 gradually takes more of the spring load and the link 32 is gradually unloaded while the common link 84 rotates slightly in a counterclockwise direction. Upon further rotation, the short links 82, 78, and 80 associated with main link 32 collapse to accommodate for the physical displacement of the associated parts while the linkage including link 36 exerts a continuing restraining and returning force from spring 34 upon crank 12 and the associated door.

In the initial portion of the operation in the reverse direction, the counterclockwise rotation of common link 84 continues until link pivot 95 is directly lined up in a straight line between the crank pivot 85 and the link pivot 93. Again, link 96 and the common link 84 essentially behave as a single link after main link 36 takes all of the tension force from spring 34. The operation of these parts will be further elaborated upon below in conjunction with the explanation of FIGS. 3 and 4.

When the linkage of main link 36 is in tension, the link 92 is held tightly against the body of crank shaft 12, and essentially forms a crank arm of crank shaft 12 having an effective crank arm pivot at 93.

FIG. 2 is a side view, partly in section, of the embodiment of FIG. 1 with the cover in place. Referring more particularly to FIG. 2, the spring 34 is arranged between the crank member 86 and an anchor plate 100 which fixes it to the bottom 58 of the casing 10. Both the crank 86 and the anchor plate 100 are constructed with open center bores so that they can be fitted over and positioned upon a common shaft 102. The shaft 102 is supported at its bottom end in a suitable depression in the bottom 58 of the casing as shown in dotted outline at 104. The upper end of shaft 102 is firmly positioned by engagement within a suitable opening in the cover member 60, as shown at 106. The crank arm 86 is freely rotatable upon shaft 102 (under the restraint of the force of spring 34). However, near the bottom portion of shaft 102 it is provided with a pin 108 which engages in associated slots in the hub of the anchor plate 100. In order to provide an initial loading force upon the spring 34, the anchor plate 100 may be rotated in a counterclockwise direction by rotation of the shaft 102 transmitted through pin 108. In such rotation, one or more teeth shown at 110 provide a ratchetlike engagement with one or more corresponding teeth formed in the bottom 50 of the casing to thereby provide a. desired amount of initial spring tension adjustment. As indicated in FIG. 1, the upper end of shaft 102 may be provided with a hexagonal center opening which will receive a corresponding wrench having a hexagonal cross section by means of which the shaft 102 may be rotated to apply the initial spring tension through the operation of ratchets 110. This may be accomplished as a routine installation or servicing operation by inserting the wrench through a suitable opening in the cover 60 which may be provided with a closure 112 shown in FIG. 2. Since shaft 102 does not rotate during normal operation of the apparatus, the closure 112 may simply consist of a sheet metal cover held in assembled relationship on the main cover 60 by means of a machine screw which may threadedly engage in a center hole of shaft 102 tapped into the bottom of the hexagonal wrench hole previously described.

The cover member 60 may also be provided with threaded cover plugs 114 and 116 which can be easily removed to allow access to the needle valves 44 and 46 for easy adjustment of the operation of the system. Corresponding individual covers may also be provided for access to the needle valves associated with ports 64 and 66.

FIG. 3 is an enlarged detail top view of the spring 34,

the crank 86, and portions of the tension linkages including main links 32 and 36 as shown in FIG. 1. An added optional feature is shown in FIG. 3 consisting of a shim member 118 attached to the tail portion of common link 84 by means of a machine screw 119, and having a body portion 120 positioned between the tail portion of common link 84 and the adjacent inner surface of main link member 32. This provides a small clockwise rotational displacement of the common link 84 away from the main link 32, and thus provides for a slight effective lengthening of the linkage including main link 32, and a concurrent shortening of the linkage including main link 36 to accomplish a fine adjustment in the closed position of the associated door. As previously explained above, when the door is closed and at rest, the linkages including main links 32 and 36 share the force of spring 34, both linkages being under tension. Under these conditions, the respective ends of links 32 and 36 associated with pivots 81 and 95 are each tightly pulled against their respective sides of the common link 84. The tension force in link 32 tries to rotate the common link 84 in a clockwise direction, while the force in link 36 tries to rotate common link 84 in a counterclockwise direction. Pivot 95 is located at a greater radius from pivot of the common link 84 than is the pivot 81. Therefore, the tension force in link 36 operating at pivot has a greater moment arm for rotation of common link 84 than does the tension force in link 32 operating through the pivot 81. Thus, common link 84 is normally rotated in a counterclockwise direction when the door is at rest until the tail portion of common link 84 rests against the inner side of main link 32 as illustrated in FIG. 1. When the shim 118 is fastened to the tail portion of common link 84, the same rotational moments cause the body portion of the shim to be pinched between the tail portion of common link 84 and the inside surface of main link 32 to provide the new rotational position of the common link 84 as illustrated. By providing shims 118 of different thicknesses, and by moving the shim, as provided by its slotted screw connection to common link 84, so as to be positioned either closer or farther away from the pivot 85, fine adjustments of the door position may be accomplished.

It is one of the important features of the present invention that, because of the sharing of the tension forces of the spring 34 by the linkages including main links 32 and 36, and because the tension load is gradually taken up by link 32 and released by link 36, for instance, as the door begins to open, the initial resistance to the opening operation of the door is substantially less than is encountered in prior systems. Furthermore, it will be apparent that by providing a greater lateral separation in the rest positions of pivots 81 and 95, the portion of the rotational are of the door during which the full tension load is gradually released by link 36 and assumed by link 32 may be increased as desired. Thus, the geometry of the common link 84 and the associated links 32 and 36 and their intermediate linkages can be modified in many ways to accomplish varying results in terms of the distribution of these forces and the angle of door operation over which the reduced force is effective. An alternative construction in which a greater lateral separation between pivots 81 and 95 is provided is illustrated in FIG. 4.

In FIG. 4, components having exact counterparts in FIG. 3 are given the same reference numbers. Parts which have been changed or modified have been given the same reference numbers with the added suffix letter A. It will be realized from the prior explanations of FIGS. 1 and 3, that the modification of FIG. 4 provides a substantially greater angle of rotation of common link member 84A in the initial movement of the door before link 36A gives up all of its tension force to link 32A. Since pivots 81A and 95A are equally distant from the common link pivot 85, the rotational forces about these two pivots are equalized so that the tail of the common link 84A is not definitely biased against either one of the main links 32A or 36A. However, this structure is stabilized in a particular centered position by providing the tail, or lower portion, of common link 84A with sufficient width to completely fill the space between the two main links 32A and 36A. Thus, the rotational position of common link 84A is definitely fixed when the door is in the closed position. In the operation of the linkage structure of FIG. 4, when the door is opened under power, as the tension is increased in link 32A and decreased in link 36A, the resultant clockwise rotation of the common link 84A causes the pivot 95A to swing outwardly away from the body of common link 84A so that the inner surface of the main link 36A bears upon the rounded corner 122 of the common link 84A. Conversely, for reverse operation of the door, when the common link 84A rotates in a counterclockwise direction, the inner surface of main link 32A bears upon the rounded corner 124 of the common link 84A. In this phase of operation, the corners 122 and 124 provide a new effective pivot point for the associated main link. The distance of these respective corners of the common link 84A from the pivot 85 is a significant factor in determining the operating characteristic in the transfer of the tension forces between main links 36A and 32A during initial opening movement. These characteristics may also be modified by providing additional link pivots at the corners 122 and 124, or by simply shortening the tail portion of the common link 84A. These and other useful modifications to this portion of the apparatus for obtaining desired opening force characteristics will be apparent to those skilled in the art.

FIG. is an enlarged detail view of a portion of the cylinder block 40 adjacent to the cylinder 20 and particularly illustrating the details associated with the vent shut ofl valve 56. As previously explained above, when hydraulic fluid under pressure is supplied through pipe 22, the ball check valve 42 opens to admit that fluid to cylinder 20 to initiate the movement of piston 18. To prevent loss of fluid from cylinder 20 through vent ports 48 and 50 associated with the needle valves 44 and 46, the vent shut off valve 56 is provided. Valve 56 is simply a ball valve which is exposed on its left side in the drawing to the full incoming hydraulic pressure fluid through the passage 57 from the input line 22 ahead of the check valve 42. For this purpose, the fitting 38 is provided with a circumferential groove at 128, and one or more radial holes 130 communicating from the interior of the fitting to the groove 128. The circumferential passage formed by the groove 128 communicates with the passage 57, which is simply a hole bored in the cylinder block 40. The incoming pressure of the hydraulic fluid applied through passage 57 to ball valve 56 forces that ball valve to the right into the closed position as shown against a valve seat formed by a bushing 132. The bushing 132 may simply be press fitted into the valve bore of the cylinder block 40.

When the ball valve 56 is in the closed position as illustrated, and when the full supply pressure is applied through passage 57, then that pressure is applied to an effective piston pressure area corresponding to a circular area having a diameter equal to the ball diameter. On the right side of the ball 56, it is subjected to essentially zero (ambient) pressure over an area corresponding to the inside cross-sectional area of the vent passage 54 through the bushing 132. The remainder of the piston area of the ball valve 56 at the right side communicates with the common vent passage 52 and it is ultimately subjected to the full hydraulic fluid supply pressure available within cylinder 20. However, the effective piston area of the ball piston 56 to which this pressure is applied is equivalent to a circular area corresponding to the full ball diameter, less the circular area corresponding to the center opening diameter of the bushing 132. Thus, the net force on the left side of the ball 56 is substantially greater than the net force on the right side of ball 56 during the power stroke part of the operation of the system While hydraulic pressure fluid is being supplied through pipe 22. Therefore, the common vent passage 52 remains closed and there is no dissipation of hydraulic pressure fluid from the vents associated with valves 46 and 44 during the power stroke.

The initial movement of the ball valve 56 to the closed position is quite positive and stable. The initial surge of hydraulic pressure fluid, as it begins to move through the pipe 22 generally operates to close the ball valve 56 at the same time it is opening the ball check valve 42. However, the ball valve 56 will positively close even if it is open after cylinder 20 is pressurized. The port associated with valve 46 provides a restricted passage for the flow of hydraulic fluid. Accordingly, there is a pressure drop in the fluid as it bleeds from the cylinder 20 into the discharge passage 52. Therefore, even if the ball valve 56 could be said to have the full pressure from passage 52 applied to its right side before it closes, that pressure would not be equal to the closing pressure applied at passage '57. Furthermore, whenever the valve 56 remains open, by even the slightest amount, that opening causes the discharge of fluid. from passage 52 through the vent 54 and thereby reduces the pressure applied to the right side of the ball piston 56. Thus, the ball piston 56 closes positively and remains closed as long as the pressure fluid is applied through pipe 22. This result is accomplished Without biasing springs for piston 56. Thus, the piston 56 may be referred to as free-floating.

Upon the return stroke of the piston 18, the check valve 42 is closed and the hydraulic fluid pressure source is stopped or disconnected so that the pressure within the passage 57 drops. The pressure force within the common vent passage '57 is then suflicient to move ball valve 56 to the left to open the discharge port 54. The rate of discharge is then controlled substantially entirely by the opening of the valves 44 and 4 6. The construction of the ball valve 56 and its associated parts is very simple, but also very effective.

While the ball 56 is preferred as the valve element in the above-described structure, it will be apparent that the valve cylinder can be extended farther into the cylinder block, shortening passage 57, and a cylindrical piston may then be employed in place of valve ball 56, the piston having a spherical surface, or a conical needle-like surface at the right end thereof which seats upon the bushing 132.

If there is no requirement in the system that the capacity of the fluid pressure source. must be conserved, the ball valve 56 and its associated connecting ports may be omitted, and the outlets from the valves 44 and 46 may be vented directly through the side of the cylinder block in a manner similar to that indicated in FIG. 1 for ports 64 and 66 at cylinder 30. That construction is simpler and more economical in first cost.

While this invention has been shown and described in connection with particular preferred embodiments, it is apparent that various changes and modifications, in addition to those mentioned above, may be made by those who are skilled in the art without departing from the basic features of the invention. Accordingly, it is the intention of the applicant to protect all variations and modifications within the true spirit and valid scope of this invention.

I claim:

1. A spring restrained door control system comprising a pivoted shaft arranged to be connected to the door for rotation during swinging movement of the door, said shaft including crank arms arranged on opposite sides thereof, a separate collapsible tension linkage connected to each of said crank arms and extending away from said crank arms in substantially the same direction, each of said collapsible linkages being operable for controlling the rotation of said shaft in a direction opposite to the direction controlled by the other of said linkages,

wherein the improvement comprises a single spring member,

both of said tension linkages being connected to said single spring member,

said spring member being connected to maintain both of said tension linkages in tension at a centered position of said shaft corresponding to a closed position of the door associated with said shaft,

said linkages being respectively operable to apply a tension force between the associated crank arm and said spring member upon rotation of said shaft in each of the two respective rotational directions,

each of said linkages being arranged to collapse whenever said shaft is moved in a direction opposed by the tension in the other of said linkages.

2. A system as claimed in claim 1 wherein there is provided at least one pressure fluid piston connected by means of a connecting rod and a crank arm to said shaft, a cylinder block defining a cylinder for confining said piston and operable to retard rotation of said shaft and the associated door towards the closed position of the door from one of the open positions thereof.

3. A system as claimed in claim 2 wherein said cylinder associated with said piston includes connections for the admission of fluid under pressure from a source of pressure fluid for causing operating rotation of said shaft by means of fluid pressure upon said piston.

4. A system as claimed in claim 3 wherein said cylinders are defined by a common cylinder block and wherein said cylinder to which the pressure fluid connections are provided is arranged with vent ports communicating with a common discharge passage within said cylinder block, and a valve arranged to automatically close said discharge passage whenever fluid under pressure is supplied from the source to the cylinder to thereby prevent loss of pressure fluid through said discharge passage during the operation of the associated piston in response to the pressure fluid.

5. A system as claimed in claim 2 wherein a second retarding piston is provided for retarding the rotation of said shaft during closing movement of the associated door from the other open position thereof.

6. A system as claimed in claim 5 wherein said cylinders are defined by a single cylinder block, said cylinder block being provided with cylinder vent ports extending transversely directly from the interior of at least one of said cylinders to the exterior of said cylinder block.

7. A system as claimed in claim 1 wherein a means is provided for gradually shifting tension force from one of said tension linkages to the other of said tension linkages upon initial movement of said shaft away from the closed door position.

8. A system as claimed in claim 7 wherein said means for gradually shifting tension from one of said linkages to the other comprises a common link pivotally connected to said spring member and pivotally connected to each of said linkages.

9. A system as claimed in claim 8 wherein the connection of said common link member to one of said tension linkages is at a greater distance from the pivotal connection of said common link member to said spring member than is the connection of said common link member to the other one of said tension linkages, said tension linkage connections to said common link member comprising pivotal connections laterally spaced apart so that the tension linkage having the greater spacing of its connection to said common link member exerts a greater rotational moment upon said common link member to positively return said common link member to a rotated-at-rest position corresponding to a desired door closed position of said shaft.

10. A system as claimed in claim 9 including an adjusting shim positioned between said common link member and a link of the one of said tension linkages having the lesser rotational moment upon said common link member to thereby adjust the door closed position of said shaft.

11. A system as claimed in claim 8 wherein said ten sion linkages are connected to said common link member at laterally spaced pivot points at substantially equal distances from the pivotal connection of said common link to said spring member.

12. A system as claimed in claim 11 wherein said common link member includes a tail portion extending between said tension linkages to maintain a well-defined rotational position of said common link member in the closed door position of said shaft.

References Cited UNITED STATES PATENTS 1,637,575 8/1927 Kushlan et al 49-334 X 2,789,814 4/1957 Carlson 49-137 2,911,210 11/1959 Ferguson 49-137 3,084,927 4/1963 Linder 49-264 3,319,380 5/1967 Loftus 49-137 3,369,323 2/1968 Millard et al. 49-334 X DENNIS L. TAYLOR, Primary Examiner US. Cl. X. R. 49-334; 92-68 

36. SPRING 34 MAINTAINS THE DOOR IN A CENTERED CLOSED POSITION AS SHOWN. THE DOOR MAY BE POWER OPERATED BY FLUID APPLIED TO CYLINDER
 20. DURING POWER OPERATION RETURN CONTROL VENTS FROM CYLINDER 20 ARE CLOSED BY BALL VALVE
 56. 